1. Field of the Invention
This invention relates to a hydrosilylative composition comprising an acrylic, polyester or epoxy resin having an aliphatic unsaturated bond, a compound having a silylidyne radical and a hydrosilylation catalyst such as platinum and a hydrosilylation reaction process of subjecting the former two compounds to hydrosilylation reaction in the presence of the catalyst. More particularly, it relates to a hydrosilylative composition and process which permit a hydrosilylation reaction to readily proceed even in a system which contains or contacts with catalyst poisons.
2. Prior Art
It is well known that acrylic, polyester or epoxy resins having an aliphatic unsaturated bond and compounds having a silylidyne (.ident.SiH) radical undergo a hydrosilylation reaction in the presence of hydrosilylation catalysts such as platinum or rhodium series catalysts whereby curing takes place through addition of the silylidyne radical to the unsaturated bond. There were proposed in the art a variety of curable resin compositions which cure through such hydrosilylation reaction.
Since the hydrosilylation reaction is high in reactivity, curing of resin compositions through hydrosilylation reaction has the advantage that the compositions cure uniformly both at the surface and the interior and with a minimal volume loss. Another advantage is that an overall process from the mixing of components to form a composition to the end of curing is energy saving.
Owing to these advantages, coupled with availability in liquid form and ease of handling without a need for special equipment or techniques, the curable resin compositions now find widespread use in a variety of fields. For example, these compositions are used for electrical insulation, mold patterning, junction coating, optical fibers, LIMS molding, silicone gel, release paper, and tackifiers.
However, the hydrosilylation reaction is sensitive to catalyst poisons. More particularly, if such elements as N, P, S, Sn and As, even in trace amounts, are present in the compositions, or if such elements are present in substrates to which the compositions are coated and cured, then these elements become catalyst poisons to considerably inhibit the hydrosilylation reaction. A retarded hydrosilylation reaction can result in short curing.
It is therefore a common practice to carry out the hydrosilylation reaction while utilizing suitable catalyst poison scavenging means. That is, catalyst poisons can be removed from the composition itself or the substrate to which the composition is coated and cured, for example, by pretreating the components of the composition with activated carbon or by heat cleaning the substrate to pyrolytically decompose off the catalyst poisons. It is also possible to carry out the hydrosilylation reaction by raising the reaction temperature to enhance the activity of the hydrosilylation catalyst or by increasing the amount of the hydrosilylation catalyst added.
These approaches, however, are disadvantageous both in process and economy. It is thus desired to ensure that the hydrosilylation reaction proceeds even in the presence of trace amounts of catalyst poisons.
The inventors proposed in Japanese Patent Application Nos. 277645/1991 and 276965/1991 to subject a composition based on an aliphatic unsaturated group-containing resin to a hydrosilylation reaction with organohydrogen-polysiloxane for crosslinking. This composition tends to experience short curing when contacted with crosslinked melamine or urethane coatings. There is a desire for improvement in this respect.
In the coating field, some examples of crosslinking resin compositions through hydrosilylation reaction in a system containing such an element as N, P, S, Sn and As or a system in contact with a material containing such an element are known. Such known solutions include a curing system in which the hydrosilylation reaction is combined with another distinct curing system and a coating system of laying two coats in a single baking step.
In the former composite curing system, the other curing system distinct from the hydrosilylation reaction is, for example, a curing system based on an addition reaction of a hydroxyl-containing resin with a polyisocyanate or a block thereof and a curing system based on an addition reaction of a carboxyl-containing resin with an epoxy-containing resin. In these systems, alkyl ether melamine resins, polyisocyanate and amine compounds (e.g., tributyl-ammonium bromide) used as a catalyst for reaction between carboxyl and epoxy groups form nitrogeneous components. Also phosphates, sulfonates (e.g., para-toluenesulfonate), and tin compounds (e.g., dibutyltin dilaurate) used as a reaction catalyst for the curing system form components containing P, S or Sn. These systems do not drive the hydrosilylation reaction forward.
One known example of the latter system, that is, coating system of two coats/one bake is a metallic base coating/clear coating system. This is the case when the clear coating uses a system of curing through the hydrosilylation reaction and the base coating uses a curing system distinct from the hydrosilylation reaction. However, hydrosilylation reaction is inhibited if the base coating contains a catalyst poison.
There is a desire to have a coating technique capable of driving the hydrosilylation reaction even in the presence of or in contact with such catalyst poisons.
Therefore, an object of the present invention is to provide a hydrosilylation reaction composition and process which permit a hydrosilylation reaction to proceed without inhibition even in the presence of trace amounts of catalyst poisons including such elements as N, P, S, Sn and As.